PROJECT SUMMARY Atherosclerotic cardiovascular disease (ACVD) is the leading cause of mortality and disability worldwide, even in optimally treated patients. While the impact of many immune cell types on atherosclerosis is well- established, the contribution of CD8+ T cells to the disease pathology remains to be further elucidated. In previous work using unbiased single-cell (sc) analyses to study the immune composition of human atherosclerotic plaques we found new dysregulations tissue resident memory (TRM) CD8+ T cells associated with clinical CV outcomes. CD8+ T cell infiltrates have been described in both early and advanced human atherosclerotic plaques and their cytotoxic effector functions contribute to plaque progression in mice. However, information on how CD8+ T cells contribute to atherosclerotic plaque vulnerability and cardiovascular (CV) events is limited and remains to be fully understood. In preliminary sc studies, we identified the transcriptional regulator Zeb 2 as a top candidate master regulator of plaque CD8+ T cell proatherogenic alterations. We hypothesize that Zeb2 is a key driver of the activation and cytotoxicity of effector TRM CD8+ T cells in atherosclerotic plaques and that these alterations contribute to disease progression and plaque vulnerability. We also contend that its downregulation is implicated in the reprogramming of PD-1+ TRM CD8+ T cells found in plaques of patients with recent stroke. We propose two independent aims to study the role of Zeb2 in plaque vulnerability and CV events. In Aim 1, we will dissect the Zeb2-mediated activation of plaque TRM CD8+ T cells and determine their association with plaque vulnerability at pathology. In this Aim we will also determine the effect of Zeb2 deficiency selectively in activated TRM CD8+ on atherosclerosis in mice. In Aim 2, we will identify how Zeb2 mediates TRM CD8+ T cell dysregulations of adverse CV outcomes and determine how Zeb2 downregulation in all CD8+ T cell affect their exhaustion reprogramming and whether these alterations contribute to plaque size and vulnerability in vivo. These studies will address important gaps in knowledge in CD8+ T cell biology in atherosclerosis, and will tackle previously unappreciated cellular and molecular mechanisms associated with plaque rupture/erosion that may contribute to clinical CV outcomes. We foresee that this information may help guide the future design of precise, molecularly targeted immunotherapies to prevent CV outcomes in patients with carotid and coronary disease.